SUMMARY

SUMMARY

IDENTIFICATION

SCIENTIFIC NAME(s)

Portunus pelagicus

SPECIES NAME(s)

Blue swimming crab, Flower crab

In Thailand, P. pelagicus is distributed along the coasts of both the Andaman Sea (west) and the Gulf of Thailand (east) and is presently perceived and managed as a single unit. However recent analysis of genetic diversity and population differentiation originating from Ranong, Suratthani, Krabi, Prachuap Khiri Khan, and Chanthaburi suggested that BSC from these five different areas are regarded as different genetically isolated populations and should be treated as separate management units (Klinbunga, 2007). But this study only included one sample in the western coast, so one management unit is assumed given the lack of information..

ANALYSIS

The stock status for the offshore fishery appears to be in a reasonable condition;

Information systems are in place, but there is limited information on fleet structure, especially in coastal fisheries;

Research activities would appear to be in place, but it is unclear how comprehensive this may be across the range of the fishery;

There are reasonably strong engagement processes that deal with endangered, threatened or protected (ETP) species interactions and promotion of environmental awareness;

Governance structures are in the process of development with an amended Royal Ordinance in draft; and

The national fisheries strategy confirms application of the precautionary principle an ecosystem approach to fisheries management, but these have yet to be adopted in practice.

Weaknesses

From (MRAG 2017)

Stock status is likely to be over exploited for the fishery as a whole, but heavily over exploited in coastal areas;

Limit and target reference points have not been set nor incorporated into management;

There are no fishery specific harvest strategies, nor rules in place;

There are some localised management measures in place, including crab banks and voluntary no take zones, including the preservation of crab habitat (sea grass beds). These are by no means widespread throughout the coastal communities, but evidence suggests that initiatives such as these are being encouraged;

There is limited information on fleet structure;

There is limited data on retained and bait fish species affected or applied by the two fishing methods – traps and bottom set gill nets; and

There is no fishery specific management plan in place nor supporting management systems that would ensure appropriate management actions would be implemented.

Compliance by fishers is an issue

FISHSOURCE SCORES

Management Quality:

Management Strategy:

< 6

Managers Compliance:

< 6

Fishers Compliance:

< 6

Stock Health:

Current Health:

< 6

Future Health:

< 6

RECOMMENDATIONS

RETAILERS & SUPPLY CHAIN

Participate in and promote research to determine the stock structure throughout the Thailand.

Develop and implement a stock assessment programme to assess all stocks based on the best available science, and develop appropriate stock-specific management advice.

Press regulators to develop and implement a management plan (including a harvest strategy and reference points) and fully enforce existing regulations in all areas. The management plan should be sensitive to regional differences in the stocks, fisheries and socio-economic needs.

Implement product specifications and/or a Control Document to help address specific sustainability or compliance issues in the fishery (e.g. undersized or berried crabs entering the supply chain).

Establish a comprehensive data collection programme that includes bycatch and non-target species catch (both ETP and non-ETP species), as well as information on habitats and ecosystem.

FIPS

Thailand blue swimming crab - bottom gillnet/trap:

Stage 4, Progress Rating A

CERTIFICATIONS

No related MSC fisheries

Fisheries

Within FishSource, the term "fishery" is used to indicate each unique combination of a flag country with a fishing gear, operating within a particular management unit, upon a resource. That resource may have a known biological stock structure and/or may be assessed at another level for practical or jurisdictional reasons. A fishery is the finest scale of resolution captured in FishSource profiles, as it is generally the scale at which sustainability can most fairly and practically be evaluated.

Analysis

OVERVIEW

The stock status for the offshore fishery appears to be in a reasonable condition;

Information systems are in place, but there is limited information on fleet structure, especially in coastal fisheries;

Research activities would appear to be in place, but it is unclear how comprehensive this may be across the range of the fishery;

There are reasonably strong engagement processes that deal with endangered, threatened or protected (ETP) species interactions and promotion of environmental awareness;

Governance structures are in the process of development with an amended Royal Ordinance in draft; and

The national fisheries strategy confirms application of the precautionary principle an ecosystem approach to fisheries management, but these have yet to be adopted in practice.

Weaknesses

From (MRAG 2017)

Stock status is likely to be over exploited for the fishery as a whole, but heavily over exploited in coastal areas;

Limit and target reference points have not been set nor incorporated into management;

There are no fishery specific harvest strategies, nor rules in place;

There are some localised management measures in place, including crab banks and voluntary no take zones, including the preservation of crab habitat (sea grass beds). These are by no means widespread throughout the coastal communities, but evidence suggests that initiatives such as these are being encouraged;

There is limited information on fleet structure;

There is limited data on retained and bait fish species affected or applied by the two fishing methods – traps and bottom set gill nets; and

There is no fishery specific management plan in place nor supporting management systems that would ensure appropriate management actions would be implemented.

Compliance by fishers is an issue

RECOMMENDATIONS

Last updated on 24 September 2018

Recommendations to Retailers & Supply Chain

Participate in and promote research to determine the stock structure throughout the Thailand.

Develop and implement a stock assessment programme to assess all stocks based on the best available science, and develop appropriate stock-specific management advice.

Press regulators to develop and implement a management plan (including a harvest strategy and reference points) and fully enforce existing regulations in all areas. The management plan should be sensitive to regional differences in the stocks, fisheries and socio-economic needs.

Implement product specifications and/or a Control Document to help address specific sustainability or compliance issues in the fishery (e.g. undersized or berried crabs entering the supply chain).

Establish a comprehensive data collection programme that includes bycatch and non-target species catch (both ETP and non-ETP species), as well as information on habitats and ecosystem.

1.STOCK STATUS

STOCK ASSESSMENT

Last updated on 27 January 2018

The Thai national government through it’s DoF department conducts assessments and complies data on Blue swimming crab. While there are some regional assessment, the stock structure for blue swimming crab (BSC) is not well understood. Other bodies have indicated that BSC is over exploitered particularly in coastal waters (Banks 2011)(Drabanandana et al. 2017)(Kunsook et al. 2014)(MRAG 2017)(Sawusdee and Songrak 2009)(Taylor 2013).

SCIENTIFIC ADVICE

Last updated on 27 January 2018

Because BSC is under a FIP a number of improvements have ben suggested to decrease the exploitation and to rebuild this stock (MRAG 2017)(NFI 2016). More recently (Kunsook et al. 2014) suggested closing areas during the spawning season, implementing minimum sizes, restocking, and protecting habitat. Some of these measures are in the planning stage but have yet to be implemented (fisheryprogress 2017) Overall there is no publicly available information on catch or exploitation advice from the Thai DoF .

Results from stock assessment in Sikao Bay (Trang Province) showed that the asymptotic outer carapace width was 17.30. The asymptotic inner carapace width was 16.70 cm and its curvature was 1.5 per year. The total mortality coefficient was 8.96 per year, natural mortality coefficient was 1.61 per year and fishing mortality coefficient was 7.35 per year. The exploitation rate was 0.82. The total stock of blue swimming crab at first catch at 2.5 – 3.0 cm was 7,895,170 individuals. Results of stock assessment also showed that the maximum sustainable yield was 364.33 tons, maximum economic yield was 25.29 million Baht (1 Baht = US$ 0.033) and total biomass was 139.83 MT (Suwasdee et al 2009).

However there are no overall reference points for the stock at a national level, though such are in the works (Banks 2011)(fisheryprogress 2017)(Taylor 2013)).

CURRENT STATUS

Last updated on 27 January 2018

Because of a lack of assessment information either regionally or nationally, the overall status of BSC in Thailand cannot be determined relative to reference points. The consensus from multiple sources is that the stock of BSC in Thailand is near or at overexploitation (Banks 2011)(Drabanandana et al. 2017)(Drabanandana et al. 2017)(fisheryprogress 2017)(Kunsook et al. 2014)(MRAG 2017)(Taylor 2013) with some indicating that removals exceed natural productivity. The more heavily fished in-shore areas are thought to be more exploited then the off-shore region, while off-shore the status may be more resonable (Banks 2011)(MRAG 2017).

The blue swimming crab is a commercially important species in Thailand. However, the yield from this species has drastically decreased due to over harvesting. In addition to being severely exploited, the stock has suffered from habitat degradation and non-selectivity of fishing gears, which tend to remove most of the size classes from the population. Ten percent of the hooked crabs are spawning, with 700,000-1.4 million fertilized eggs each. Stock assessment in Trang Province suggested that at present, the exploitation of BSC in the Trang coastal area is higher than the recruitment (Suwasdee et al 2009).

Data on a national level confirms the above trend, with a reduction by nearly half of landings nation-wide since 2000.

2.MANAGEMENT QUALITY

MANAGEMENT

Last updated on 27 January 2018

While there are some regional measures including gear restrictions, seasons, size and trap limits, there is no comprehensive national management of this stock (Banks 2011)(MRAG 2017). However, such management measures are in the planning stage as part of the ongoing fishery improvement project (fisheryprogress 2017)(NFI 2016).

Lacking an overall stock status, assessment or management plan at a national level, there appears to be little in the way or management action to rebuild the stock. As part of a fishery improvement project, there are efforts, however to increase the stock (fisheryprogress 2017)(NFI 2016). The Crab bank, a re-stocking program, is underway.

COMPLIANCE

Last updated on 27 January 2018

Crab fishery has been mainly practiced by small-scale fishers who have low education and income for more than three decades. Majority of small-scale fishers rely on income from crab fishery and they try to catch crab as much as possible at any size of crab. Therefore, the implementation of mesh size limit measures is hardly accepted by them and result to failure of management (Nitiratsuwan, et al 2009). Interview with the fishers also implied that the stock could also be harmed by the fishers’ preference for catching spawning females, especially egg-bearing females, as they provide higher biomass than other crabs (Trisak, et al. 2009).

Overall compliance with measures is thought to be low (Banks 2011).

3.ENVIRONMENT AND BIODIVERSITY

BYCATCH

ETP Species

Last updated on 27 January 2018

While interactions with Dugongs is relatively rare (Banks 2011)(Taylor 2013) interactions with endangered turtles are thought to be problematic, particularly in the trawl fishery (Taylor 2013). Data, overall, from either at-sea observation or log books are lacking (Banks 2011)(Drabanandana et al. 2017)(Taylor 2013).

Other Species

Last updated on 27 January 2018

Collapsible trap is a major type of fishing gear for catching the blue swimming crab. The trap also catches other finfish and shellfish species including the small size of economical species, which can be associated with the discard problem (Taylor 2013).

In addition to that, the collapsible pots can be accidentally lost at sea, and continue to catch target and non-target species. The ghost fishing study was conducted by quantified number of entrapped animals and estimating the mortality through the simulated experiment. The simulated pots caught of 7.1 individuals of toad fish, 5.6 sea urchins and 5.5 ridged swimming crabs/pot/year. Other 19 species were also entrapped such as spiral melongena, filefish, catfish, etc. Total number of killed animals was calculated as 20.1 individuals/pot/year. Five pots continued to catch in the second year, which indicated that they have potential to keep the capture function for extended periods until losing the function due to accumulation of bio-fouling at the pot entrances (Boutson, et al 2008).

More resent research has also concluded that ghost fishing by this gear type can be problematic and should be investigated (Banks 2011)(Drabanandana et al. 2017)(Taylor 2013)

HABITAT

Last updated on 27 January 2018

The trawl fishery in particularly is prone to habitat impacts (Banks 2011)(MRAG 2017)(Taylor 2013), but little data is available to support or refute impacts of other gear types on habitat. It should be noted that measures to identify and management for potential impacts are in the planning stages, but are not yet implemented (fisheryprogress 2017)(MRAG 2017)(NFI 2016).

There are some protection of seagrass areas and dugong habitat where gillnet, trawl, and pushnet prohibited to fish in these areas. However, the enforcement is an issue in some areas since many small fishing boats involved (Banks 2011). Thailand has a number of Marine protected areas (Prasertcharoensuk et al. 2010) though their effectiveness is hampered by lack of enforcement and compliance.

ECOSYSTEM

Blue swimming crabs (BSC) can be an important trophic pathway. These crabs and other crabs consume small benthic infauna and are preyed upon by skates, rays, and other fishes (Banks and Trumble 2011)(Taylor 2013). As such that can represent a trophic link between benthic and pelagic ecosystems (Banks and Trumble 2011)(Taylor 2013). However little information in the exact role in the Gulf of Thailand is not well documented. Some studies looking at the overall effects of fishing pressure in the region have been conducted but these are now outdated (Taylor 2013).

FishSource Scores

Last updated on
27 January 2018

MANAGEMENT QUALITY

As calculated for 2017 data.

The score is < 6.

Management objectives and target reference points are lacking in most areas.

As calculated for 2017 data.

The score is < 6.

While management measures including reference points and others sometimes set on a regional level, there is no overall management plan. Such a plan, however, is in the works.

As calculated for 2017 data.

The score is < 6.

Compliance with existing regulations is weak and enforcement is inefficient.

STOCK HEALTH:

As calculated for 2017 data.

The score is < 6.

According to multiple sources the resource is overexploited and catches have declined as a result.

As calculated for 2017 data.

The score is < 6.

Fishing mortality is not available for a large portion of the unit, but consensus among multiple sources indicates that it is overexploited particularly in inshore areas.

Some information on gear impacts to the sea bed and sensitive habitats is available (Banks 2011), but direct observation of the effects of fishing in the area of fishing have not been well studied (Banks 2011)(MRAG 2017)(Taylor 2013).

Information on priority habitats as well as fishing locations and gear interactions is poor, but under study (Banks 2011)(MRAG 2017)(Taylor 2013).

Some measures, such as limiting gear use and fishing in eel grass habitats is in place. However, enforcement and compliance is problematic (Banks 2011)(MRAG 2017)(Taylor 2013).​

Older modeling work and survey information does provide some insight into ecosystem structure and function, but the impacts of the fishery itself have not been studied (Banks 2011)(MRAG 2017)(Taylor 2013).

Some information on ecosystem structure and function is available. Though outdated, it does define a reference state prior to 1980 which has not been adopted by management(Banks 2011)(MRAG 2017)(Taylor 2013).​

While some measures such as protection of eel grass beds and exclusion of gear types by area are in place, compliance and enforcement is problematic (Banks 2011)(MRAG 2017)(Taylor 2013).​

To see data for management quality, please view this site on a desktop.

To see data for stock status, please view this site on a desktop.

DATA NOTES

There is high uncertainty in stock structure and an overall assessment, reference points, national quota, and other measures is lacking. Public sources of regional assessments were not available. As such scores 1-5 were determined qualitatively.

Landings are national landings (both coasts) from FAO in 1,000s of tons